Birth Rate

Birth rate is a measure that quantifies the number of births in relation to population size. Births, deaths, in- and out-migration are important components of population change. An essential but not inclusive measure of the population change is the birth rate. The crude birth rate (CBR), which is the simplest measure of natality, is usually calculated by dividing the number of live births in a population in a given period (usually one year) by the average or midyear population size multiplied by a constant K (usually 1,000). The numerator is usually obtained from birth registers, which vary in completeness and accuracy from one country to another, whereas the source of the denominator is the census or population estimate. Under reporting of births and deaths is more common in developing countries than in developed countries.

An example of calculating crude birth rate:

Natural increase of a population refers to the difference, whether positive (surplus) or negative (deficit), between births and deaths in a population. Natural increase = births – deaths for a specific population in a given time.

Measures of fertility include age-specific fertility rate, which is the most suitable statistical measure for detailed comparison between different populations, because it is not affected by different age composition. It is defined as the number of births to women in a given age group divided by the number of women in the same age group multiplied by a constant. General fertility rate (GFR) is the number of live births per 1,000 women of childbearing age (usually 15–49 years); the total fertility rate (TFR) is the average number of children born to a women throughout her reproductive years. TFR is a robust measure of fertility that is not affected by the age structure.

Among the factors affecting birth rate are the current age-sex structure, religious beliefs especially concerning contraception, economic status, women's social status, female literacy levels, and general education. Improving the last four factors usually leads to a decline in birth rates. The issue of anticontraception religious beliefs is very sensitive and should be approached cautiously to avoid undesirable community reactions. However, birth control programs that do not tackle these factors are not effective unless they are enforced by a central government with a strong antinatalist policy.

Birth rate is also an important indicator of demographic transition, which starts with a decline in mortality rates and birth rates. However, the mortality decline precedes the fertility decline, leading to a rapid population growth during the transition period. In midyear of 2006, the estimated world birth rate was 21 per 1,000, whereas for the more developed countries it was 11 per 1,000, and for the less developed countries it was 23 per 1,000.